Hawaii Massage License Practice Exam

Which group of muscles assists in trunk flexion?

1. Spinal Extensors

2. Rectus Abdominis

3. Lower Back Muscles

4. Quadratus Lumborum

The correct answer is: Rectus Abdominis

The rectus abdominis is the primary muscle group that assists in trunk flexion. This long, flat muscle is located in the front of the abdomen and runs vertically from the pubic bone to the lower ribs. When the rectus abdominis contracts, it helps to pull the ribcage closer to the pelvis, thereby facilitating movements such as bending forward or performing sit-ups. This muscle plays a crucial role in core stabilization and is vital for various activities that require forward bending or flexion of the trunk. Other muscle groups, while important for different functions, do not primarily contribute to trunk flexion like the rectus abdominis does. For instance, spinal extensors are involved in extending the spine, while lower back muscles provide support and stability for the lumbar region but primarily assist in extension and lateral movements. The quadratus lumborum also contributes to stabilizing the pelvis and spine but does not assist significantly in flexing the trunk forward. Thus, the rectus abdominis is specifically responsible for the action of trunk flexion, making it the correct answer.